Voicemail Question

I’ve installed AsteriskNow to get a quick and proper installation, but my goal is to understand the Asterisk system from the command prompt. With that in mind I’ve created a couple of Xlite endpoints using SIP.CONF and Externsions.CONF and they will call and talk to each other just fine. I’m now experimenting with the voicemail system. I’ve set up the voicemail.conf and and added to the extensions.conf and according to the CLI the extensions go to voice mail but I can’t hear the greeting or anything. From reading other posts this is typically a symptom of a codec mismatch. My question is, where are the greetings, busy, unavailable messages stored? I’ve read the comments in the config files and looked at the example 1234 extension directory structure, but the voicemailboxes created by extensions.conf don’t have the gsm sound files in them. Any ideas? Thanks